Trapped heat shortens the life of the roof above it and pushes your cooling bill up underneath it. It is the part nobody sells you and everybody needs.
Heat with nowhere to go does damage in both directions.
A very hot upstairs, an attic like an oven, high cooling bills, or premature wear on the roof surface.
Often yes. Depends on the roof type and shape.
It reduces how much heat pushes into the house, so the air conditioning works less.
Yes. It is part of a proper install and warranties generally require it.
Read the reviews yourself, on whichever site you already trust.
Pick a time that works. We come out, get on the roof, take photos, and give you a real number. No charge either way.